Persons trapped in an elevator car which is stalled between floors of a building should remain in the car and await help by trained technicians. Some persons may attempt to force the doors of the car open in an effort to escape. This can be extremely hazardous if the car is not at or close to a landing at which the floor of the elevator is at the same level as a floor of the building. Persons attempting to jump to or climb to a hallway of the building under this circumstance may fall into the hoistway or elevator shaft. Accidents of this kind are prevented by restrictor systems which prevent opening of the elevator car doors from inside the car if the car is not at or close to a landing at a floor of the building.
Restrictor systems of the above discussed kind have some form of latching or locking member that is not accessible to occupants of the elevator car and which must be retracted to enable opening of the door of the car. Sensing means produce a signal at times when the car is at or close to a landing and an electrical actuator retracts the latching or locking member in response to the signal.
The sensing means can be an electrical switch carried by the elevator car and which is operated by contact with members which are fastened to the hoistway wall or an elevator guide rail and which are situated along the path of travel of the switch. Switches of this kind deteriorate from wear, are prone to breakage and require frequent inspection and replacement. To avoid this problem many recent door restrictor systems have photoelectric sensors which detect the location of the elevator car relative to the landings in the building. An infrared light emitter and an infrared detector are carried by the car and are directed towards the elevator guide rail or the hoistway wall. Strips of infrared reflecting material on the guide rail or hoistway wall are positioned to reflect infrared from the emitter back to the detector at times when the elevator car is at or is close to a landing.
Prior elevator door restrictor systems using photo-electric sensing of the above described kind require undesirably frequent maintenance operations as the reflective members gradually acquire a coating of dust and/or other airborne particulates that reduces the reflectivity of the members. This makes it necessary to clean or replace the members at frequent intervals to assure reliability of the system. After a period of time, the reflective tapes can peel off from the surface to which they were affixed.
The present invention is directed to overcoming one or more of the problems discussed above.